Relationships between bridging oxygen O quadrupolar coupling parameters and structure in germanates
نویسندگان
چکیده
We have performed ab initio calculations on the model cluster (OH)3Ge±O±Ge(OH)3 in order to re®ne the relationships between O quadrupolar coupling parameters and the local structure around the bridging oxygen. From these calculations the trend in the bridging oxygen O quadrupolar coupling constant, Cq, and asymmetry parameter, gq, with changing Ge±O±Ge angle was found to be similar to previously established trends in silicate clusters with the overall Cq values being systematically increased in magnitude by approximately 3 MHz. Such a shift can be attributed to dierences in cation±oxygen distances as well as coordinating cation electronegativity. In addition, we also investigated the eect of changing intratetrahedron bond angles over a range that has been suggested to exist in germanate systems. While such variations in intratetrahedron bond angles lead to a small variation in Cq, gq remains relatively unaected. In such cases, gq can still be a reliable probe of Ge±O±Ge angle while Cq could serve as a probe of tetrahedron distortions. Ó 2000 Elsevier Science B.V. All rights reserved.
منابع مشابه
Antimalarial Activity of some Conjugated Arylhydrazones: Ab Initio Calculation of Nuclear Quadrupole Coupling Constants (NQCC)
“Malaria” is a life-threatening blood disease in tropical regions that spreads by the bite of the Anopheles mosquito. Antimalarial medications are designed to cure or prevent this infection, and prosperous achievements in this area mostly depend on the knowing the drug-receptor interactions and active sites of medicine. This improvement can be achieved through understanding the electronic struc...
متن کاملA theoretical study of benzaldehyde derivatives as tyrosinase inhibitors using Ab initio calculated NQCC parameters
Tyrosinase is a multifunctional copper-containing enzyme. It can catalyze two distinct reactions of melanin synthesis and benzaldehyde derivatives, which are potential tyrosinase inhibitors. To find the relationships between charge distributions of benzaldehyde and their pharmaceutical behavior, the present study aimed at investigating nuclear quadrupole coupling constants of quadrupolare nucl...
متن کاملMQMAS NMR studies of zeolite HY
High-resolution O multiple-quantum MAS (MQMAS) NMR spectra have been obtained for zeolite HY in order to study its local structure and Brønsted acidity. The O NMR signals due to all the different oxygen environments have been observed in one single experiment, including the readily-resolved signals arising from the two types of oxygen atoms of the zeolite framework (Si–O–Al and Si–O–Si), and ox...
متن کاملInvestigating the Effects of Molecular Oxygen Impurity on the Quadrupole Coupling Constants of Boron Nitride Nanotubes: Computational Studies
Density functional theory (DFT) calculations have been performed to investigating the effects of themolecular oxygen impurity on the quadrupole coupling constant (Qcc) parameters of armchair and zigzagboron nitride nanotubes (BNNTs). Optimization processes have been performed to relax the original andimpure structures of the investigated BNNTs. Afterwards, the Qcc parameters have been evaluated...
متن کاملEffect of Additives on Mn/SiO2 Based Catalysts on Oxidative Coupling of Methane
The Oxidative Coupling of Methane (OCM) over M-Na-Mn/SiO2 catalysts (M=W, Cr, Nb and V) was investigated using a continuous-flow quartz reactor at 775°C, 1 atm and 100 cm3min-1 gas flow rates, and correlated with the observed structure and redox properties.The interaction effects of the metal-metal and metal-support on the...
متن کامل